I have been thinking about some of the details of interrupt handling in Net=
BSD, which are probably not architecture-specific, and I have 3 questions=
 I have been thinking about below.

1. Can interrupt handlers be interrupted by higher priority handlers or do =
they run to completion?

2. If 1. is possible, is it also possible for the handler to interrupt itse=
lf i.e. is it possible to make the handler reentrant if the proper interr=
upt masking via spl functions is not done?

3. For SMP machines, it is possible for multiple instances of the same hand=
ler to be running on different CPUs e.g. if the hardware generates an int=
errupt while the handler is running on a CPU and another CPU services the=
 interrupt?

Are the answers to these questions the same for BSD 4.4 or is NetBSD signif=
icantly different (and if they are not different, where can I find the an=
swers for BSD 4.4)?